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LRU Cache.java
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79 lines (72 loc) · 1.55 KB
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class LRUCache {
Node head;
Node tail;
Map<Integer, Node> map;
int capacity;
public LRUCache(int capacity) {
head = new Node(-1, -1);
tail = new Node(-1, -1);
head.next = tail;
tail.prev = head;
map = new HashMap<>();
this.capacity = capacity;
}
public int get(int key) {
if (!map.containsKey(key)) {
return -1;
}
int val = map.get(key).val;
moveToFront(map.get(key));
return val;
}
public void put(int key, int value) {
if (!map.containsKey(key)) {
if (map.size() == capacity) {
evictKey(tail.prev);
}
Node node = new Node(key, value);
map.put(key, node);
node.next = head.next;
head.next.prev = node;
head.next = node;
node.prev = head;
}
else {
map.get(key).val = value;
moveToFront(map.get(key));
}
}
private void moveToFront(Node node) {
Node prev = node.prev;
node.next.prev = prev;
prev.next = node.next;
node.next = head.next;
head.next.prev = node;
node.prev = head;
head.next = node;
}
private void evictKey(Node node) {
Node prev = node.prev;
node.next.prev = prev;
prev.next = node.next;
map.remove(node.key);
}
}
/**
* Your LRUCache object will be instantiated and called as such:
* LRUCache obj = new LRUCache(capacity);
* int param_1 = obj.get(key);
* obj.put(key,value);
*/
class Node {
int key;
int val;
Node next;
Node prev;
public Node(int key, int val) {
this.key = key;
this.val = val;
next = null;
prev = null;
}
}